1. Field of the Invention
The invention relates to a stator and a motor provided with the stator. More particularly, the invention relates to an improvement of the structure of a stator having a stator core formed from a plurality of split cores arranged in a circumferential direction.
2. Description of the Related Art
A motor has a rotor, and a stator that is arranged around the rotor. The stator has a coil. When current passes through this coil, a rotating magnetic field is consequently generated. The electromagnetic action that operates between this rotating magnetic field and the rotor causes the rotor to rotate.
The stator has a stator core that has a hollow cylindrical shape. In order to improve manufacturing efficiency, including the efficiency of forming the stator core, there is an example of the stator core being formed from a plurality of split cores arranged in a circumferential direction. A stator core formed in this way is manufactured by inserting the split cores that have been arranged in the circumferential direction into the inner periphery of an annular cylindrical body, and then shrink fitting this cylindrical body.
Japanese Patent Application Publication No. 2009-148050 (JP-A-2009-148050) describes a stator having a stator core formed by a plurality of split cores arranged in a circumferential direction. In JP-A-2009-148050, heat deformation of the split cores is suppressed such that roundness on the stator core inner peripheral side is stabilized by including a surface that is orthogonal to the axial direction on a portion where adjacent split cores abut against one another, and welding the split cores together at this surface.
In the process of inserting the split cores into the cylindrical body and shrink fitting the cylindrical body, which is a manufacturing process of the stator core described above, the split cores are clamped and secured by heat shrinking the cylindrical body. At this time, the temperature distribution of the entire cylindrical body is uneven, so the clamping force on the split cores from the cylindrical body during heat shrinking also ends up being uneven. As a result, the uneven clamping force may cause the split cores to come out of position, which would adversely affect the roundness on the inner peripheral side of the stator core. Although it is possible to make the clamping force even by adjusting the temperature of the entire cylindrical body, doing so would increase the size and complexity of the device, and end up increasing manufacturing time and cost.